This invention relates generally to hand-held dispensers for viscous or liquid products, and more particularly to dispensers of the type wherein a separate container having an upstanding neck is fitted with a two-part cap construction comprising a screw cap, and a base part which latter is adapted to be secured to the container neck by means of retention beads, or else alternately screwed in operative position where threads on the neck and base part are provided. In such dispensers, the base part and container normally remain together during shipping and use of the dispenser. The screw cap is held captive on the base part but is moveable thereon between sealing and discharge positions.
Dispensers of this type are well known. Examples of such dispensers are illustrated in the following patents, which are believed to constitute a representative sample of the prior art currently in existence: U. S. Pat. Nos. 3,370,764; 3,598,285; 3,406,880; 3,407,967; 3,216,630; 3,351,249; and 3,319,843, all issued to Morton B. Stull; and U. S. Pat. No. 4,477,002, issued to Gene Stull.
Dispensers of the type described and illustrated in the above patents were frequently employed with substances such as adhesives or glues of one type or another, which were for the most part, non-volatile. That is, problems associated with some of the material gasifying while still in the container were normally not encountered. Accordingly provision for dealing with build-up of excessive pressures was not made, since there was generally no necessity for doing so, and the chances of such containers bursting or breaking along a seam were minimal.
It has been found that with other types of substances, however, namely certain foods, there exists a strong tendency for gas to build up within the container after a period of time. The problem is especially troublesome with the category of foods which includes mustards. With conventional packaging where an adequate seal was employed in order to insure the integrity of the product, there have occurred instances where the container has either burst, or else the caps thereof have been blown off by the pressure in the container. In the case of mustard, such an occurrence represented not only a loss of the particular dispenser involved, but in addition, the contents often were splattered with considerable force against adjacent containers, giving rise to the need for removing them from the area where the accident occurred, cleaning them individually, and replacing them. The clean up represented an unnecessary waste of time as well as being a nuisance, as can be readily appreciated. Practically all of the containers of which I am aware do not make provision for the venting of built-up gas inside the container, since in general the manufacturers and distributors are more concerned with the integrity of the package, that is, making sure that the contents are not contaminated by external means, and also that no leakage of the product occurs during the interim between the filling of the dispenser and the purchase and use by the consumer.